Acid copper plating



United States Patent 41c O -E K PL N Leon -R. :Westbrook, Solon, Ohio NoDrawing, Application September 25, 1957 Serial No. sseow '19 Claims. c1.294-52 The present invention relates generally to the electroplating artand is more particularly concerned with novel compositions for usein'aqueous acid copper electroplating baths,..vvith-;,novel. baths ofthis type having unique and b epronerliesfat d wit Process fortrodepositing copper involving the use 'of said compositions and-bathsand affording special new advantages and results.

Copper, plated from the usual acid bath compositions, is dull andcrystalline in appearance, and exhibits poor throwing power of the bath,in that recessed areasof an irregularly-shaped surface are not uniformlycovered .bymthe. coppendeppsitf l'flie principal functional differencebetween, cid copper baths. and coppercyahideplatv.ing formulations; isthat the former havej/ery poor throw- ,ing or covering power, while thelatter ar'feiice'llent j, in both of these prap'erties; My. inventionprovides an additivecombination' to acid copper plating baths thatpermits them to compete commercially with copper cy- ,anide baths v vith respect to throwing and covering powe i while retaining the wellrecognized operating. advantagesbf the'f acid 'baths. Thus, my inventionprovides an acid copper plating bath-that isicor'nmercially competitivewith the cyanide bath with respect to uniform covering power, and vthatprorluces a deposit having superior physical properties such as luster,uniformity and smoothness of' surface, ease of tbufling' to a brightfinish and homogeneity of structure. ---'lhe-deposits from my new andnovel bath composition are particularly suitable for use as bases forsubsequent nickel plating, especially for-use prionto pla t ing from themodern bright nickel Modern chromium plated finishes are underlaid withelectroplate s of copper and nickel, respectively, on the base metalsuch as-steel, fonexamplel I'In, this sequence it is important to,provide a copper plate of superior ..physical properties such as,unlformi coverage, a very fine crystal structure, smooth, lustroussiirface, dense homo- .geneous, structure,. duetility and. easeofbuffing. Even :yvithall their well known deficiencies, cyanide platingbaths have. generallyibeen .used for this purpose, because acidbathsjcouldihot produce the quality ofdeposit re quired. Cyanide "copperplating baths usually operate at high temperatures,' are"extremely toxicand unpleasant to operate, require additionagents that produce rinsingproblems and interfere with adhesion of the subsequent nickel deposit,produce copper deposits Ithat are difficult to bulf to a satisfactory.finishand, like all cyanide.

plating baths, require expensive waste disposal systems for thedestruction 'of cyanide in rinses and tank wastes to v9 str am rel stisaa d s a contamination, which is becoming" an increasingly pressingindustrial problem.

BecauseYof these'difiicultie's, man'y'attempts have been made to developan acid copper plating bath to produce 1 copper deposits or superiorphysical properties for .use

under nickel: plating.

None of these attempts have i been. entirely successful.

- All depend of; bath addition agents'of varioustypes, some 2,931,750-Patented Apr. 5, 1950 ice of which produce brittle deposits, some arenot stable in thebath, requiring excessive additions and breaking down.into deleterious decomposition products that must be removed from theplating bath frequently by carbon treatment, and some are not stable attemperatures much over 90 F., requiring bath cooling and therebyrestricting the operating current densities and hence the producvec'apacityof the bath.

I have now found a combination of addition agents,

which, when present in commercial acid copper plating baths, producebaths of superior covering power, are

stable at high operating temperatures, form no deleterious decompositionproducts, and produce copper deposits of superior physical properties,as defined above, that are eminently suited for use under subsequentnickel de- .posits from either conventional or proprietary bright Vties.

nickel plating baths. For convenience and to avoid rep etition, thecopper plates produced by the baths and processes. of this inventionwill hereinafter be referred to as copper deposits having superiorphysical proper- These valuable results are obtainable now for the firsttime because of my surprising and unpredictable discovcries upon whichthis invention in all its various aspects is predicated, One of the morebasic of these discoveries is that certain organic compounds actsynergistically in combination with chloride ion in aqueous acid copperplating baths to produce electrolytes having unique Qcharacteristics andcopper depositshaving superior physicalprop'erties, 'as described above.I'have also found that this synergistic effect is not limited to aparticular plating bath composition but is obtainable in all commercialacid copper plating baths. However, the con- ,centration of thechloride'ion' must be controlled within 1 a narrow range and there is acritical minimum amount of or concentration of the organic compound inthese baths;

Still further, I have found that except for the bromide ion in certainbath additives and bath composiftions of this invention, the chlorideion has no equivalent inits present synergistic effect. There are,however,

. a. numberof satisfactory sources of chloride ion for this purposealthough all chlorides are not suitable and some may be quite harmful tocopper plating operations. Sim- 'ila'rly, I have found. that the organiccompounds contem- QpIated by'thi's invention can be classified and thatthere are a relativelyflarge number of these compounds which may 'beused successfully in these new baths and copper plating, operations.

In fact, l have found that special advantages are to be obtained byusing mixtures of these compounds in the bath additives and plating bathcompositions of this invention.

These new acid copper electroplating baths, briefly and generallydescribed, contain a bath-soluble polyalkyl- Qtives contemplated by thisinvention can be classified as polyalkylene oxides .with 'or withoutterminallysubstituted radicals. Compounds of this general type arewidely used in industry and their methods of preparationare matters .ofrecord, being disclosed in several US. patents, among. which may becited 1,970,578; 1,922,459; 2,059,273; and 2,213,477. .They arediscussed by Stau dinger in Die Hochmolekularen OrganischenVerbindungen, 1932, page 287 et seq.

More specificallv the organicadditives contemplated v and undesirablecopper deposits.

by this invention may be represented by the general formula R-(CH CHO),,H

in which R is the hydroxyl radical (OH) in the case of n is a numericalvalue greater than 5.

In order to simplify the nomenclature of this document and avoidneedless repetition, the compounds represented by the above generalformula that are contemplated by this invention will be referred to aspolyoxyethanols,

. and will include the unsubstituted polyethylene oxides as well asthose having a terminal substituent, as set forth in detailsubsequently. Since the molecular weight of the ethylene oxide group (CH O) is 44, it follows that a the polyoxyethanols of this invention willhave calculated molecular weights over 300, the actual figures dependingon the values of n and the molecular weights of the substituentradicals.

Polyoxyethanols are stable in acid copper plating baths and form nodeleterious decomposition products, thus eliminating this cause forfrequent purification of the bath by carbon treatment. Similar compoundshave been proposed for use in electro-plating baths, notably by Hofimanfor tin plating baths in US. Patent 2,457,152 and by Rochl for lead-tinalloy baths in US. Patent 2,734,025.

Surprisingly enough, the presence of polyoxyethanols in conventionalcommercial acid copper plating baths produces highly undesirable resultsunless to these baths t is also added bath-compatible compounds thatproduce in solution the chloride ion within specifically controlledlimits of concentration. By the term bath-compatible is meant bathsoluble compounds containing chlorine combined with anions that areeither inert or harmless in the acid copper plating bath, such as, forexample, hydrogen chloride, sodium chloride, cupric chloride, ammoniumchloride, lithium chloride, potassium chloride, and in fact the chlorideof any anion that will not codeposit with copper from an acid bath noradversely affect the deposition of copper from such a bath.

It may be noted here that the chloride ion is not a conventionalconstituent of commercial acid copper plating baths, nor is copper everplated commercially from a chloride bath. In fact the chloride ion isgenerally considered undesirable as a constituent of commercial acidcopper plating baths because it lowers the burning range, that is, itaccentuates the tendency to form burned or dark, coarsely crystallinedeposits at the higher current densities, thus lowering the operatingcurrent density range with consequent loss in the production capacity ofthe bath. For this reason, every effort is made to keep chlorides out ofcommercial baths. Also the chloride ion is known to act as a poison formost of the additive agents used in acid copper plating, as it partiallyor completely nullifies their efiects, and therefore it is generallyavoided in bath using additive agents.

Thus it will be seenthat the essence of my invention resides inobtaining new, useful and unexpected results by combining in acid copperelectroplating baths, two specific types of materials, either of whichwhen present in the bath without the other, produces distinctly inferiorIt appears that the function of the chloride ion in the baths of thisinvention is to enable the polyoxyethanol to exert its beneficial efiectupon the plating reactions and the plate formation, while thepolyoxyethanol ameliorates practically completely the deleteriouseffects of the chloride ion on the copper deposit. The novel bathaddition agents or additive compositions constituting another aspect ofmy invention, succinctly stated, consist essentially of between about 10and about 90 proportional parts of polyoxyethanol, which is soluble insuch baths to the extent of at least 0.05 gram per liter, and betweenabout 90 and about 10 parts, respectively, of a bath-compatible:chloride which is similarly soluble and capable of providing a chlorideion concentration in such baths of at least 0.02 gram per liter. Thusthe additives of this invention can be specially designed to be used asmake-up additions to baths partially depleted during plating op-'erations, and will consist of these same essential sub stances butcontain them in different ratios, depending: on the identity of thepolyoxyethanols used and the re-- quirements, as explained later.

My new and novel combination of additives functions equally well in thecheaper and more common acid sulfate baths as well as in the newer andmore expensive acid fiuoborate baths. The general formulae for thesebaths are shown in Table I.

TABLE I Compositions of commercial acid copper baths Concentrations ingrams per liter (A) Sullate Bath Approx. Preterred Range C S .5H 0150-250 200 11 509. 45-110 75 (B) Fluoborate Bath Low High 225 450 ffII15 so H1130; (optional) 15 30 As a general disclosure of my invention, Icite the addition to any acid copper plating bath of the combination ofadditive agents shown in Table 11 following:

Since'the operating conditions depend on the degree and nature of theagitation employed, both mechanical and air systems being used, theabove figures for temperature and cathode current density will ofnecessity vary considerably therewith relative to' each other, all ofwhich is conventional and well known to those skilled in the art.

Considering again the general formula for the polyoxyethanols of thisinvention:

in which R is a radical derived from the group comprising phenols,alcohols, ethers, acids and amines, the general relationship between thenature of R and the value for 11 requires further discussion. In thesepolyoxyethanols, the values for n must be increased as the bathsolubility of the'compound from which R is derived decreases. This isnecessary in order to provide adequate erallydesirable for my purpose.

-shark-solubi ty.-t inc ewh e trt edrfio w er rsatv tea no it; mustbe-sufficient to dissolve; enough polyoxyethanol to produce copper"deposits ot-superior physical properties.

' :-For example, if- R-is' derived frommethyl alcohol or ahydrochloricacid, both ofwhich are highly bath soluble, a very low value for n,such-as 6-8-is satisfactory, and wisvrequired for additive actiononlyand notfor bath solubility. On the other hand, if ,Ris derived frombetanaphthol, which has a definite though low bath solubility,

-n .need be only around 11-15 to produce a satisfactory zbath solubleand effectivepolyoxyethanol, while if R is derived from octylphenol,which ,is much less, bath soluble, n should be above about 15,preferably around 1 -20 to 30 to produce a-.polyoxyethanol of adequatebath solubility and effectiveness. .And ifR is' derived from a highlybath insoluble amine, suchas for example, dehydroabietylamine, n shouldbe over about .40 toobtain a satisfactory .polyoxyethanol. .Itshould beunderstood of course that this discussion. applies; to polyoxyethanols(that are capable of producing optimum results in ,combinationwith thechloride ion. Less completev but still a useful results can be obtainedby. using corresponding -polyoxyethanols of lower n value, in which casethey may have lower bath solubility and hence'lessv activity in thebath. It is also sometimes desirable, as explained later, to usemixtures ofpolyoxyethanols in which n is lower than optimumfor a singlecompound, hence the difiiculty of specifying a particulanvalueorlimiting range of values for n for anygiven-substanceis apparent.

It will be noted that the structure of the general formula is similar tothat of commercial surfactantsofthe --nonionic type, in which thevaluefor-n .is generally in I the low-range specified for the polyoxyethanolsof this invention. It is also well known that as the value for n;increases in such products, their surface activity diminadvantageous incompounding additive mixtures for commercial applications to useselectedmixtures of the polyoxyethanols contemplated by this inventionThus the difficulty of specifying an exact value or a limiting range ofvalue for n in the case. of polyoxyethanols containing substituentradicals is apparent. In such cases however,

- becaujse of the bath solubility factor, I generally prefer h to use arelatively high value for r of the order of 20-60,

although for reasons that are readily apparent, I do not desire to be solimited.

, The amount of polyoxyethanolsrequired in solution in the plating bathmay vary somewhat with the nature of the substituent radical. In generalit is desirable to use .theminimum concentration consistent withsatisfactory results or to produce the effects .desired and maintainconsistent operating conditions. In the case of polyoxytethanolscontaining substituent radicals this concentration has been found to bearound 0.1 to 0.5 gram per liter, preferred being 0.2-0.3 gram perliter. in the case of the unsubtituted polyoxyethanols somewhat higherconcentrationsmay be found desirable. In both cases, substituted andunsubstituted, a reasonable excess of polyoxyethanols in the bath doesno harm. Baths containing various concentrations of variouspolyoxyethanols up to as high as- 30 grams per liter have been-operatedsuccessfully. "However such high concentrations are unnecessary, andmight be consideredundesirable in some cases onths.generalprinciplethat; theless organic matterpresent-in; a plating baththe, better. T Oiie lof-.the desirable features of this invention, froma functional standpoint, is the low concentration of organic additiveconstituent required to produce satisfactory results.

Table III following illustrates some oftheorganic compoundsfrom which Rof the general formula has been de rived to make polyoxyethanolscontaining substituent radicals and which have been found satisfactoryfor. the

- purposes of this invention.

TABLE III 'Approximate optimum Phenols: 1 range for n Phenol V 10-30Octyl phenol -40 Nonylphenol -50 Beta-naphthol 12-30 Ethers:

' Biphenylether 15-40 Disecondary butyl phenyl ether 20-40 Alcohols:

Methyl alcohol 6-25 Sorbitol p 20-40 Lauryl alcohol 20-40 Acids:

Hydrochloric acid 6-20 Caproic acid 20-60 Oleic acid 20-60 .Stearic acid7 20-60 Rosin acids 20-60 LAbietic acid 20-60 Amines:

j Ethylene. diamine -60 Rosin amines 40-60 Dehydroabietylamine 40-60Tertiary-alkyl primary amines The foregoing-Table III is illustrativeonly and by no means complete as will be evident from a perusal of thereferences hereinbefore cited'covering the preparation of this type ofcompounds. It should also be noted that the values given for n areapproximate optimum values only. They are shown for purposes ofillustration only, and are in no way limiting for reasons already cited.

Theunsubstituted type of polyoxyethanols that have been found mostsatisfactory for the purposes of this invention are those in whichn ofthe general formula is about 10 or greater and R is the hydroxylradical. These materials have calculated molecular weights in excess ofV 600, and maygo as high as 20,000. One that I have found to beparticularly satisfactory has a calculated molecular weight around 6000and n approximates 135. As

illustrative of this type of polyoxyethanols thoseshown in Table IVcompare average molecular weight with calculated approximate values forn.

It should be realized that in the case of these unsubstitutedpolyoxyethanols .as well asv inthe case:of-..the polyoxyethanols with asubstituent radical, the'commereial ,products aremixtures of compoundsthe; molecular weights of which vary within commercial limits ofmanufacture and purification, hence the figures given in this documentfor molecular weights are average values only and therefore the valuesfor n can only be approximate and also representing average values.

The particular advantage of the unsubstituted type of polyoxyethanols isthat they offer all the advantages of synergistic additive action withthe chloride ion without lowering the surface tension of the bath,therefore can be used either alone or in mixtures with the substitutedtype of polyoxyethanols, some of which do lower the surface tension ofthe bath, so as to regulate the surface tension effect as desiredwithout adversely affecting additive action, as previously mentioned.This permits control of pitting on the deposit when encountered, withoutproducing excessive foaming from air agitation.

Ingeneral, a littlemore of the unsubstituted polyoxyethanols can be usedto advantage, and I prefer around 0.5 gram per liter of bath, although Ihave used as high as 30 grams per liter with excellent results and noill effect.

One commercial line of the unsubstituted type of polyoxyethanols nowavailable is offered by the Carbide and Carbon Chemicals Company underthe designations polyethylene glycols and carbowaxesf Of these, I preferto use Carbowax 6000 at a bath concentration around 0.5 gram per liter.

As for the other essential ingredient in my new and novel combination ofadditives for acid copper plating baths, the chloride ion and thebromide ion are practically equivalent and are unique among cations asbeing the only ones that work synergistically with my organicpolyoxyethanols to produce the copper deposits having superior physicalpropertiesresulting from this invention. Further, the critical amountsof chloride ion and bromide ion are the same on a chemical equivalent ormolal basis. Thus the values given for the chloride ion can be convertedto values for the bromide ion by multiplying by the ratio of thechemical equivalent or molecular weights: 79.9/ 35.5 or approximately2.25. The chemical equivalent on a molal basis in each case correspondsto a range of 0.00055 to about 0.028 mol of either chloride ion orbromide ion. The bromine salts that are bathcompatible and effective inthe baths of this invention correspond to the chlorine salts statedabove to be suitable or preferred for use herein, on a chemicalequivalent or molal basis.

Contrary to what might be expected, none of the acids or salts of theother two halogens have the synergistic effect of this invention.However, this effect can be obtained by using mixtures of chlorides andbromides as long as the aggregate of chloride and bromide ions in theplating bath is within the aforesaid critical range for chloride aloneon a molal equivalent basis and as long as there is no interactionbetween the chloride and bromide compounds or with other bathconstituents resulting in the formation of substances having detrimentaleffect upon the copper plating operations or the resulting products.

In its method aspect this invention in general comprises the step ofadding to an acid copper electroplating bath prior to its use abath-compatible chloride and thereby establishing a chloride ionconcentration in the bath of between 0.02 and about 1.0 gram per liter,and also adding to the bath a polyoxyethanol of molecular weight greaterthan 300 and thereby establishing in solution in the bath an amount ofsaid polyoxyethanol effective to act synergistically with the. chlorideion to produce uniform copper deposits of superior physical properties.

It is also a process of this invention to maintain in the plating bathsynergistic quantities or concentrations of chloride or bromide ion andpolyoxyethanol. This involves the step of periodically adding to thebath a makeup quantity of one or both the synergistic constituents orcompounds which function as sources of said chloride ion orpolyoxyethanolin solution. In preferred practice the additions will bein the form of mixtures specially prepared for restoring depleted bathsand containing therefore between about 10 and about proportional partsof polyoxyethanol and between about 90 parts and about 10 proportionalparts of bath-compatible chloride.

The novel combination process or method of my. invention comprises ingeneral the preparation of the plating bath containing the synergisticquantities of organic compound and chloride ion, electro-depositingcopper from the bath, and as the bath becomes depleted of synergisticamounts of said organic compound and chloride periodically adding amake-up amount of the depleted bath' substituents.

The chloride ion can be added to the bath in theform of anybath-compatible compound as hereinbefore explained. For convenience Iprefer to use hydrochloric acid, sodium chloride or cupric chloride. Thechloride concentration that I prefer to maintain is around 0.1 gram ofCl per liter. This can be done by frequent bath analysis, the proceduresfor determining chloride being simple and well known to those skilled inthe art, and a bathcompatible chloride added as required. The preferredconcentration is not critical, but should not be allowed to drop below0.02 gram of Cl per liter which I consider to be the extreme lowerlimit. For safe, flexible operation I prefer to keep the chlorideconcentration above 0.05 gram of Cl per liter, usually around 0.1 gramof Cl per liter. There is no operational advantage to be gained inmaintaining the chloride concentration over 0.1 gram of Cl per literexcept possibly to minimize the analytical control operations, howeverit does no harm to the cathode deposit to have the chloride as high as1.0 gram of Cl perliter. However, as the chloride content of the bathexceeds (about) 0.5 gram of Cl per liter, there is a growing tendencyfor the anodes to polarize, especially at high current densities, andthis anode effect is the limiting factor in setting and maintaining themaximum practical operating chloride concentration.

Chloride is eliminated from the bath at the anode in the form ofinsoluble cuprous chloride (CuCl) which precipitates in the anodesludge. The rate of chloride elimination varies greatly with chlorideconcentration,

anode current density and bath temperature, but once determined for agiven installation, it can serve as a basis for chloride replacement,thus diminishing the number of analyses required. Under averagecommercial operating conditions I have found the rate of chlorideprecipitation to be of the order of 0.01 ounce of chloride per amperehour per 1000 gallons of bath.

Since the polyoxyethanols of this invention are bath stable and only thechloride of my combination of additives is lost by anodic precipitation,it is possible to operate a bath containing adequate concentrations ofpolyoxyethanols for considerable periods of time by periodic additionsof chloride to replace that which is lost. Such bath operation isconsidered to be within the scope of this invention.

Acid copper plating baths in which the chloride ion is maintainedbetween 0.02 and 1.0 gram of chloride per liter in order to secure thesynergistic effects of organic additive agents are new and novel and inthemselves constitute one phase of this invention.

The following Examples l-7 inclusive specifically illustrate some of thepreferred formulations of my invention:

'in less or greater amounts as convenient. -polyoxyethanols may be usedat higher concentrations nxaitppn a .jfirarnsperfl ter CuSO .5H O 2 H204 V r HC1 (100%) I v v I 0.1. Polyoxyethanol in which R is the OH groupand ,n approximates 135 0.5

EX MPLE 3 CuSO .5H O ,-200 H 50 V {/5 'NaCl p 0.17 Polyoxyethanol inwhich R=octylphenyl ands ,r approximates 30 0.3

EXAMPLE 4 CuSO SH O 200 1 2 4 '75 CuCl .2H O 0.25 --Polyoxyethanol inwhich R is derived from biphenyl ether and n approximates 25 0.3

EXAMPLE 5 aS, 4 i l 75 CuCl ,2H O 0.25 Polyethyleneglycol chloride 0.3

EXAMPLE 6 -H SO V -75 CUCIZZHQQ Methoxypolyethylene glycol 0.3 EXAMPLE 71-1-1,-fi--t--'1"f-r-1---r-*: uuqb c 1 t, -3 .Bo c a (op approximates 400.3

Average operating conditions for all of above, ex-

emples: --*Temperature, 0 F. 120-140 -Average cathode current-density,amperesrper -s q.' ft. 100-200 Agitation, optional.

Since commercial operators of acid copper plating baths make up theirsolutions from chemicals or conceninvention intproper proportions sothat when added to the plating bath in correct amounts it will produce acopper deposit having superior physicalproperties. I have made aconvenient liquid additive for acid copper plating baths by dissolvingin water:

i Percent Polyoxyethanol in which R is derivedfrom beta-naphthol andn=15 Q,-. 6 Cupric chloride (CuCl .2H O) 6 This mixture or liquidadditive was added to commer- -cial acid copper plating baths in theproportion of about 4 cc. per liter or about one-half fluid ounce pergallon.

*Itis apparent that more dilute or more concentratedsolutions of thecombined additives could be made and used Since some than others, whilethe chloride component of the bath is best held at around 0.1 gramchloride per liter, the ratio of polyoxyethanols to chloride will varywith the identities ofthe respective ingredients and-the concentrationsused.

awhile formulations of -the various polyoxyethanols and batheompatihleehloiidessimilar to-the above-ma? be made and, sold for;initial-'installations,- it willobserved that since the chloride is lostby anode precipitation and bath drag-out while the polyoxyethanol; is lost by drag-out only, maintenance additions shouldbe corsumption data,and such formulations will necessarily -vary considerably, but I havefound that the following proportions will fit most cases, and canserveuntil ac- ,curate proportions are worked out.

Polyoxyethanols grams per liter HCl (cone) cc. per liter....w

one-half fluid ounce per gallon of bath, in which case the.

addition would put about 0.1, gram of chloride per liter into the bath.Wide variations may be encountered in the relative rates at whichpolyoxyethanols and chloride are lost and must be replaced, hencethecompositions of cult to specify exact limits of composition for suchadditive mixtures. However it will generally be found that for allpractical purposes they will fall withinthe following range ofproportionate parts:

: Parts "Polyoxyethanols 90-10 Bath-compatible chlorides ,l0 90 Itshould be understood that these proportionate parts represent thenumerical ratio of the constituents, and if present in solution, thesefigures do not include the solvent, since it is apparent that the ratioof constituents is V the important factor, not the actual concentrationin solution, as such mixtures may be dissolved in water to anyconvenient concentration and directions furnished the plater as to howto add the solution to the bath to best advantage.

If desired, combinations of additives for initial-installation .and formaintenance comprising selected ,poly- ,oxyethanols and bath-compatiblechlorides may be compounded in theabove tabulated proportions andoffered to the plater in concentrated or dry form so that he can ;withpolyoxyethanols. For example, bath-soluble polyoxypropanols are suitablefor this purpose, producing make his own additive solutions bydissolving them,in water, or he can add them directly to the bath.

The above illustrations will make clear to those skilled in the art allthe principles involved in compounding ad'- ditive mixtures contemplatedby this invention.

' To the extent that they are sufficiently soluble in aqueous acidcopper plating baths other polyalkylene oxide compounds may be usedinstead of or together the synergistic results described above.

Wherever in this specification or in the appended claims parts,proportions or percentages are recited, reference is tothe weight-basisrather than the volume basis itbeing understood that equivalents ormodifications of,

scribed embodiments of the invention may be made without departing fromthe scope of the invention as set forth 1 in what is claimed:

What is claimed is: 1. An aqueous acid copper electroplating bathcontaining a bath-soluble polyoxyethanol having a molecular weightgreater than 300, and a bath-compatible chlophysical properties.

2. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with beta-naphthol, and abath-compatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolbeing present in solution in the bath in amount effective to actsynergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

3. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with a phenol, and abathcompatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolbeing present in solution in the bath in amount effective to actsynergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

4. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with an ether, and abathcompatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolbeing present in solution in the bath in amount effective to actsynergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

5. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with an alcohol, and abath-compatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolbeing present in solution in the bath in amount effective to actsynergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

6. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with an acid, and abath-compatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolbeing present in solution in the bath in amount effective to actsynergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

7. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having a molecular weight greater than 300 consisting ofpolyethylene oxide terminally substituted with an amine, and abathcompatible chloride providing a chloride ion concen-.

I deposits of superior physical properties.

-8. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol consisting. of vp11 unsubstituted polyethylene oxidehaving a molecular weight greater than 600, and a bath-compatiblechloride providing a chloride ion concentration in the bath of between0.02 and about 1.0 gram per liter, said polyoxyethanol being present insolution in the bath in amount effective to act synergistically with thechloride ion in the bath to produce uniform copper deposits of superiorphysical properties. 7

9. An aqueous acid copper electroplating bath containing a mixture ofbath-soluble polyoxyethanols having molecular weights greater than 300,and a bathcompatible chloride providing a chloride ion concentration inthe bath of between 0.02 and about 1.0 gram per liter, saidpolyoxyethanols being in aggregate in solution in the bath in amounteffective to act synergistically with the chloride ion in the bath toproduce uniform copper deposits of superior physical properties.

10. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having molecular weight greater than 300, and a bathcompatible com pound providing concentration in the bath of between0.00055 and about 0.028 gram mols per liter of an ion selected from thegroup consisting of chloride ion and bromide ion, said polyoxyethanolbeing in solution in the bath in amount effective to act synergisticallywith the said ion in the bath to produce uniform copper deposits ofsuperior physical properties.

11. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol having molecular weight greater than 300, and abath-compatible bromide providing a bromide ion concentration in thebath of between 0.045 and about 2.25 grams per liter, saidpolyoxyethanol being in solution in the bath in amount effective to actsynergistically with the bromide ion in the bath to produce uniformcopper deposits of superior physical properties.

12. An aqueous acid copper electroplating bath containing a mixture ofbath-soluble unsubstituted polyethylene oxide having molecular weightgreater than 600, and a bath-compatible bromide providing a bromide ionconcentration in the bath of between 0.045 and about 2.25 grams perliter, said polyethylene oxide being in solution in the bath in amounteffective to act synergistically with the bromide ion in the bath toproduce uniform copper deposits of superior physical properties.

13. An addition agent composition for use in aqueous acid copperelectroplating baths comprising as its essential ingredients betweenabout 10 and about partsof a polyoxyethanol which is soluble in suchbaths to the extent of at least 0.05 gram per liter and has a molecularweight in excess of 300, and between about 90 parts and about 10 parts,respectively, of a bath-compatible chloride which is sufficientlysoluble in such baths to provide a chloride ion concentration in thebaths of at least 0.02 gram per liter.

14. An addition agent composition for use in aqueous acid copperelectroplating baths comprising as its essential ingredients betweenabout 10 and about 90 parts of a polyoxyethanol which is soluble in suchbaths to the extent of at least 0.05 gram per liter and has a molecularweight in excess of 300, and between about 90 parts and about 10 parts,respectively, of a bath-compatible bromide which is sufiiciently solublein such baths to provide a bromide ion concentration in the baths of atleast 0.045 gram per liter.

15. An addition agent composition for use in aqueous acid copperelectroplating baths comprising as its essential ingredients betweenabout 10 and about 90 parts of an unsubstituted polyethylene oxide whichis soluble in such baths to the extent of at least 0.05 gram per literand has a molecular weight greater than 600, and between about 90 partsand about 10 parts, respectively, of a bath-compatible chloride which issufliciently soluble in 13 such baths to provide a chloride ionconcentration in the baths of at least 0.02 gram per liter.

16. In a process for the electrodeposition of copper the step comprisingeffecting electrodeposition from an aqueous acid copper plating bathcontaining in solution 0.05 gram per liter of a polyoxyethanol and abathcompatible chloride in suflicient amount to provide a bathconcentration of from 0.02 to about 1.0 gram of chloride ion per liter.

17. In a process for the electrodeposition of copper from an aqueousacid copper plating bath containing a polyoxyethanol in an amountsufficient to produce in the presence of chloride ion a copper deposithaving superior physical properties, the step of maintaining thechloride ion concentration within the range of from 0.02 to about 1.0gram per liter by adding a bath-compatible chloride.

18. The method of electroplating copper from an aqueous acid copperplating bath which comprises the steps of adding to the bath prior toits use a bath-compatible chloride and thereby establishing a chlorideion concentration in the bath of between 0.02 and about 1.0 gram perliter, adding to the bath a polyoxyethanol of molecular weight greaterthan 300 and thereby establishing in solution in the bath an amount ofsaid polyoxyethanol effective to act synergistically with the chlorideion to produce uniform copper deposits of superior physical properties,

electro-dcpositing copper from the bath, and as the btith becomesdepleted of synergistic amounts of chloride ion and polyoxyethanolperiodically adding to the bath a mixture containing between about 10and about parts of the said polyoxyethanol and between about 90 andabout 10 parts, respectively, of the said bath-compatible chloride andthereby maintaining the concentration of chloride ion and polyoxyethanolin solution in the bath in the synergistic range.

19. An aqueous acid copper electroplating bath containing a bath-solublepolyoxyethanol chloride having a molecular weight greater than 300, anda bath-compatible chloride providing a chloride ion concentration in thebath of between 0.02 and about 1.0 gram per liter, said polyoxyethanolchloride being present in solution in the bath in amount effective toact synergistically with the chloride ion in the bath to produce uniformcopper deposits of superior physical properties.

References Cited in the file of this patent UNITED STATES PATENTS2,472,393 Avallone et a1. June 7, 1949 2,602,774 Beaver July 8, 19522,742,412 Cransberg et a1 Apr. 17, 1956 2,762,762 Donahue Sept. 11, 1956

10. AN AQUEOUS ACID COPPER ELECTROPLATING BATH CONTAINING A BATH-SOLUBLEPOLYOXYETHANOL HAVING MOLECULAR WEIGHT GREATER THAN 300, AND A BATHCOMPATIBLE COMPOUND PROVIDING CONCENTRATION IN THE BATH OF BETWEEN0.00055 AND ABOUT 0.28 GRAM MOLS PER LITER OF AN ION SELECTED FROM THEGROUP CONSISTING OF CHLORIDE ION AND BROMIDE ION, SAID POLYOXYETHANOLBEING IN SOLUTION IN THE BATH IN AMOUNT EFFECTIVE TO ACT SYNERGISTICALLYWITH THE SAID ION IN THE BATH TO PRODUCE UNIFORM COPPER DEPOSITS OFSUPERIOR PHYSICAL PROPERTIES.